The invention relates to a method for improving the firedamp safety of an assembly including an internal-combustion engine for use in underground mine workings, particularly an underground locomotive.
In connection with assemblies of the above-identified type, particularly for use in hard coal mine workings, care must be taken that they be absolutely safe against firedamp explosions. This necessitates keeping the external temperature of the internal-combustion engine exhaust gas pipe below a certain given value, for example 150.degree. C. If the exhaust gas pipe is provided with a water cooled jacket, the intended cooling can be realized only incompletely and the temperature of the gases entering the environment can easily lie above the given limit temperature value. An improvement can be realized if water from a reservoir is injected into the exhaust system so that the evaporating water provides the necessary cooling for the exhaust gases. But this requires relatively complicated additional equipment which moreover demands constant maintenance. In addition, the operating personnel must constantly monitor the supply of water in the injection system so as to prevent shutdown of the machine when the temperature is exceeded due to lack of water.
With the advance of underground mining to depths of more than 1000 m, there arises the additional problem that the ambient temperature, which is already high due to the emission of heat in the form of radiation, heated cooling air and hot exhaust gases, is increased even more by heat dissipated from the internal-combustion engine of the equipment, generally a Diesel engine. Thus, according to a rough estimate, ventilation must be made available underground for an underground mine working at the rate of about 4 m.sup.3 /h per installed engine horse power. With increasing depths, making available such quantities of air becomes more and more difficult and costly. It does not matter in this connection whether the machinery in question is a locomotive or a stationary machine since the above outlined problem of firedamp safety as well as the problems of increased heat emission by the internal-combustion engine occur equally in both cases.